What effect does incorrect ignition timing have on engine operation?

Incorrect ignition timing can significantly disrupt engine performance, leading to irregular engine operation. When the spark occurs too early or too late in the compression cycle, it affects the power stroke's effectiveness. If the ignition happens too early, combustion can start before the piston reaches the optimal position, resulting in "knocking" or pre-ignition. This can lead to increased engine noise and potential engine damage. On the other hand, if the ignition occurs too late, it can cause incomplete combustion, reduced power, and rough running conditions. These irregularities can manifest as vibrations, misfires, and overall inconsistency in how the engine runs, ultimately impacting its reliability and longevity.

The other options do not accurately describe the impact of incorrect ignition timing. It does not improve efficiency, reduce engine temperature, or enhance the fuel-air mixture; rather, it introduces instability into the engine operation, highlighting the importance of maintaining proper ignition timing for smooth and efficient performance.